An input/output (I/O) circuit may be utilized for connection of one circuit, such as a processing system, to another system, device, or component. The processing system may communicate with other external or peripheral devices by sending and receiving various communication signals. These communications are typically routed through an input/output circuit.
Conventional input/output circuits may include standard complementary metal-oxide-semiconductor (CMOS) input buffers, coupled with standard CMOS output buffers. The digital signals received through the input/output circuit swing between 0 volts (V) and the supply voltage Vdd. Thus, the input/output circuit is limited to sending and receiving communication signals that have voltage levels within this range. Certain input/output circuits may include a configurable high level output driver, however, the high output level remains fixed at a single voltage. Conventional input/output circuits do not allow for programming the input path, with a reference voltage generated on-chip, to detect an input signal voltage among various selectable levels. Additionally, the input/output circuits do not allow for coupling a programmable input path with the ability to drive the output signal at various selectable output levels. Furthermore, the input/output circuits do not allow for dynamically enabling the analog and/or digital signal paths to an I/O pad without intervention from the central processing unit (CPU).